Code for creating an import and transform package

We are building a project for a client based on sharepoint. There are a number of lists in the sharepoint site. We want to build a solution that will allow us to import data into these lists from various sources. The solution would allow users to specify the file type (like comma delimited, tab delimited etc) and a mapping file which would map fields from the file with sharepoint list. The application will allow users to select a file, select a file type, then preview the data and finally import it into the sharepoint list. It should be in .net. C# is prefferred but not required.